A tire heating or vulcanizing press can include a lower tire mold part which is supported on a press stand and has an upper tire mold part to define a mold in which a raw tire, i.e. a built-up tire blank, is placed for subsequent vulcanization.
In order to avoid mispressings, the raw tire or blank must be precisely centered within the lower mold and the upper tire must be accurately aligned with respect to the lower tire mold. To meet these requirements, it is thus not only necessary to guide the upper tire mold in a precise manner but also the lower tire mold must be maintained in a centered position. Therefore, it has been proposed to affix the lower mold to the press stand by bolts.
Although this principle may seem to be sound, it has the drawback that different thermal expansions of adjacent parts are not taken into account especially when considering the operating period of the bladder press from starting until it reaches actual operational or steady-state conditions. During this period, the precisely centered position of the lower tire mold could not be maintained.